Glass Soul Cage
by GarbagePaisley
Summary: At ten, you were diagnosed with cancer, fell in love, met Death, and lost your first love. At twenty-five, you were diagnosed with cancer, fell in love with Death, and found your first love. For the past fifteen years, monsters have been trapped under Mount Ebott. It just so happens that their resurfacing coincides with your cancer returning. (Possible eventual smut)
1. Chapter 1

When you were a child, you had this recurring dream that always started the same way:

You were deep in a forest, standing in the middle of a circular clearing. Around you were stands of trees so incredulously tall that they seemed to almost touch the sun that hung overhead. The same sun that you could feel it on your skin in the dream. And the sun was strange too. It was bigger than the sun that you experienced in the waking world. Everything was bathed in an ethereal white glow. The strangest part about the sun was that it filled you with an uncanny feeling that it was alive and watching you. The glowing ball seemed to vibrate with energy in a way that reminded you of the fairies in the story books you always fell asleep reading.

In the dream, there were birds too. There were so many of them, in the brightest, most vivid colors and they sang a beautiful melody as they swooped in and out of the clearing. When you told your grandmother about the dream later, it was hard to describe just how real it all felt as you stood there in the clearing, taking everything in. You felt warm and safe and protected.

_At first._

You remembered the very first time you had the dream - that feeling of wanting to explore more of the world your subconscious had created. But the more you had the dream, the more you dreaded taking even one step forward because you knew that the second you did, the birds would stop singing.

And, even though it had been there unnoticed the whole time, you suddenly realized that you're in a cage with no escape. That safety you'd felt moments before melted away as your hands gripped the metal bars of the golden cage, and you started shaking it. Horror began to fill you as the bars grew rustier beneath your fingers. You're overcome with a sense of dread as the sun seemed to flicker and dim.

You froze as you heard a rustling from the trees and though you didn't know what was there, you knew to be afraid. It was dark, so dark, you suddenly realized. Your eyes were affixed to those trees because whatever was out there, it was getting closer. You tried again to shake the bars only to realize that you had no hands, no arms, no body.

You were simply a floating crystal in the shape of a heart.

And then you saw it. A hooded figure emerged from the forest and from beneath the black cloak, a skeletal hand stretched out towards you. Panic set in. Something _bad_ was going to happen.

The cage door opened, but you couldn't run. Instead, you just floated towards that outstretched hand. Everything hurt, your entire body… or heart… whatever it was. You could feel yourself fissure and crack as you floated forward, shards of glass hitting the forest floor, but you couldn't stop moving towards that hand. Even as it crushed you. Even as it killed you.

You always woke up from the dream right before you broke completely. How many times had you woken up in a sweat, almost convulsing from where you swore you could_ feel_ yourself still breaking. Those dreams always upset you so much that you spent days in the hospital afterwards.

Your parents weren't superstitious people, nor were they spiritual, despite the fact that magic existed in the world. To them, you were simply a sick child with nightmares, despite the fact that the night that you first had that dream was followed by the day you were diagnosed with cancer.

You were 8 when the cancer first started making itself known. You remembered the weakness, the fatigue, but your illness went unnoticed by your parents. They weren't bad people, but your family was poor and so work always took priority over a child's complaints. By the time the doctors caught it, you were almost 10.

Leukemia, it was called. You didn't know what that meant at the time, only that something was wrong with the spongy stuff inside of your bones and that you were sick. Very sick. Your treatment started right away but your parents couldn't afford the time or money that went into all of that. Or maybe they just couldn't handle it emotionally. Looking back, you couldn't be sure and they weren't around anymore to ask.

You were so lucky to have had your grandmother. There would never be another human soul as great as that woman, you were sure. She took you to every appointment, cooked for you, cared for you, loved you. She was warm and kind and everything your parents couldn't be for you. It was almost bizarre to imagine that she and your mother were related.

After your first round of chemo, your grandma offered to take you in. She had a beautiful cottage in the country with a big yard and a garden and some animals. A perfect place to recover, she'd insisted, the fresh air would do good in your recovery. You remembered fights about it and never knowing why when you were a child.

Now that you were older and understood the world better, you knew all of the protests from your parents were due to the monsters. You grew up in the city, but you didn't really see monsters growing up. Back then, the city was still segregated. Humans stayed in their own communities, behind gates meant to keep the monsters out. You remembered seeing the news reports of what happened to monsters who crossed into human neighborhoods. The memories made your skin crawl. What humans did to them made you question who the monsters really were.

But it wasn't like that in the countryside. There was more freedom there. You remember your parents saying that the country was _uncivilized_ because monsters were allowed to roam. Not that they actually did. You were sure the monsters saw those news reports too. They knew what happened when monsters overstepped their boundaries. Why would a monster risk it when it could mean death at the hands of a human?

You'd visited the countryside with your parents and little sister once every other month before you got sick, but you never saw a monster. Now that your parents' prejudices were clear to you as an adult, you were sure that the visits were so infrequent because of the monsters' presence. And when you did visit, there were always rules – no playing outside, no talking to strangers…

When you moved in with your grandma to recover, you were still too weak from the residual chemotherapy treatments to leave bed. You spent hours in bed reading books to pass the time. When that grew boring, you'd find yourself staring out the bedroom window, hoping to catch a glimpse of one of the monsters. Sometimes you'd even day dream about befriending them and having adventures like in the books you were reading.

During the first couple of weeks, seeing a monster became the obsession of the 10 year old you. Your grandma saw through it, but unlike your parents she wasn't afraid of the monsters. She had met monsters, and that thrilled you to no end. She told you stories and answered all your questions, no matter how silly.

"Can they really use magic?"

"Yes."

"Can they eat food?"

"Of course!"

"Can they fly?"

"Some can."

"Do they speak English?"

"Most do."

For hours, you would ask, she would answer. Sometimes you'd ask the same questions, over and over even though you knew the answer. In those first days, you couldn't imagine even seeing a monster. You didn't know then that not only would you meet monsters, but you would befriend them that summer. You still remembered that summer as the best time of your life. You were somewhat healthier, you had friends, freedom, your first love...

But by the end of that summer, the dream had started again. That _damn_ dream.

Once again you were sick, and then the riots broke out and the war that ended with the monsters trapped beneath Mt. Ebott.

…

Before your grandma died, she told you something you'd never forget. By then, you were mostly grown and the cancer was long gone. You'd sat at her bedside, holding her hand, knowing that at anytime she'd be gone. It was a hard pill to swallow because she was all you had – your parents were gone by then, and you didn't have the most genuine relationship with your sister.

You didn't leave her side once during her last day on earth. You sat and held her hand. When she was awake, you read her the same stories she read you when you were sick. When she slept, you just watched her. You didn't want to let her go. Couldn't do it.

Your last conversation you had still managed to give you chills. That night she woke up from a restless sleep, panting and when your eyes met, you barely recognized your grandmother. "… it was real," she rasped.

"What was?" you asked her, your heart racing as you stroked her hand to calm her down.

Her eyes looked wild. She was scared. "… the cage. He opened my cage..." And she was gone before you even had time to process what she was saying.

You'd never seen your grandmother look that terrified. It terrified you almost as much as her words. She had seen him too, she had floated towards him and he had killed her.

And the dream was _real_.

How many times had he almost killed you? How many close brushes had you actually had with death himself? No matter how many times you thought about it, it still made you shiver. There were nights when you would be lying in bed and you'd think about it and get so scared you had to jump out of bed and turn the lights on. You found yourself wondering about the dream. Were you the only one that lived to remember it? Did everyone have the dream before death? Not that you liked to get too existential about things. If the dream taught you anything, it was that life was too short for that.

Fifteen years had passed since the first time you had that dream. Almost fourteen had passed since the monsters had been trapped underground. Twelve since you'd been cancer-free. Seven since your grandma died. Time passed and life moved on.

They say that every generation has a defining moment that people always look back on and remember exactly where they were and what they were doing. When man walked on the moon, when Kennedy was shot, when the Berlin wall fell, when the planes hit the twin towers, _when the monsters resurfaced_.

Not that it was hard for you to remember that last one. You were in the hospital because the night before the monsters resurfaced, so had your dream.


	2. Chapter 2

Chapter 2

(Sans' POV)

_Present day_

The first thing Sans did when the barrier broke and he and his friends made it to the surface was close his eyes and tilt his head back to let the breeze dance across his the bones of his face. When he opened them, head still leaned back, he was looking up at the stars. Freedom.

Sans hadn't seen the surface since he was a child. Not that he'd been much a child anymore when they banished the monsters underground. The war had been short and ugly, and Sans grew up more in those few short months than he'd like to admit. That was what being a human killing machine did to a monster.

_Twenty years earlier, Summer 20xx_

The first time Sans had killed a human, Papyrus was still a baby bones. He remembered it and how scared he'd been. That morning, Sans had woken up to the sound of Papyrus crying. Crying and crying and he just wouldn't stop. His father, Gaster, had told Sans that it was because his little brother's bones were fusing. "A natural part of life for skeletons..." Gaster had assured him as they both stood over Papyrus' crib and watched him cry. "He'll be fine, Sans..."

Later, Sans would claim to his father that he'd left the apartment because he was annoyed with how noisy Papyrus had been, but even his father knew better. It was hard for Sans to listen to Papyrus cry and not be able to ease his pain. He'd tried everything to make Papyrus smile: making silly faces, reading him a book, tickling him, conjuring bones out of thin air and tossing them for their pet dog. All of the things that usually got a delighted, 'Nyeh heh!' from his baby brother. But Papyrus still cried and cried. If Sans had a heart, it would have been broken.

Finally, Sans couldn't listen anymore. He'd grabbed a book and slid his slippers on before unlocking the door and slipping outside. All of the other monster kids in the neighborhood had school which meant that Sans would be able to find enough peace and quiet to read and maybe catch a quick nap. He headed towards the dump at the edge of human and monster territory. It was where all the humans dumped the things they didn't want any longer, but to Sans it was also where he could find the coolest items for his inventions.

Sans sat down on a tattered couch and flipped open to where his book was earmarked. Technically, Sans was home schooled but since Gaster was always busy, what that really meant was that he educated himself by reading books and building things. He was currently reading one he'd taken from his dad's collection about physics. His dad had this awesome trick where he could teleport with a snap of his fingers and Sans was determined to learn it by the end of the year.

He was just falling asleep, book open on his lap, when he heard a voice calling his name. He sat up quickly and looked around. Shit. Had Gaster realized he'd sneaked out? But it didn't sound like his dad. Before he could put too much more thought into it, the sun seemed to dim. What the…? The book slid off his lap as he stood up and looked around, noting that the whole world suddenly looked black and white. Then, in the direction of the voice he'd heard moments before, he saw an orange glow. His feet started leading him, following the heart to the opposite end of the dump, to the high fence that separated humans and monsters.

The orange glow, in the shape of a heart, was hovering just on the other side of the iron gate. He stood for a moment, just watching it as he contemplated what to do. Gaster had told him a million times not to even step one toe into human territory. Humans hated monsters. They _killed_ monsters. But now that he could almost reach that orange heart, he realized _that_ it was the heart that had said his name.

Sans rolled up his sleeve and stuck his hand between to bars but the heart was still just out of reach. He strained forward, his whole arm through the fence and grimaced as the bars ground against his shoulder bone. Then, the heart just floated towards his outstretched fingers. When it was close enough, Sans closed his fist around it and yanked his arm hard through the bars so he could examine it. As soon as he did, a blood curdling scream rang out and the world turned from black and white back to color.

On the ground, just on the other side of the fence, a small human child lay. A human child who hadn't even been standing there moments before. Sans blinked down at the site in confusion, watching in shock as blood poured out of the human's eyes and ears and mouth. But how?

A door flew open and a woman ran out, sprinting towards the supine child. "MONSTER!" She screamed, scooping up the body and craddling it. "A monster killed my baby!"

Sans was too in shock to argue, to deny the accusation. More humans poured out of buildings and before Sans could process the entire situation, they were all pushing their arms through the fence to try to grab at him.

A loud pop sounded from beside Sans and he knew it was Gaster. With another pop, they were back in the living room of their apartment. Gaster dropped Sans' hand. "Grab your brother," Gaster said, looking at Sans with an anger he'd never seen before.

"But…"

"Do it now!" Gaster said more firmly and Sans was too afraid to argue. He turned around and ran towards the bedroom he shared with his little brother and lifted him out of his crib.

"come on bro..." Papyrus was still crying and now Sans could hear police sirens in the background. "d-dad..." Sans began as he carried the infant back towards the living room. Gaster gave him a look and Sans knew better than to keep talking. With another pop, they were suddenly in a room that Sans had never seen before.

"Gaster," a commanding voice spoke and when Sans turned towards it, he saw a tall goat monster dressed in purple robes. Sans was home-schooled, but even he knew who the monster was. Asgore. The king of all monsters.

"Your majesty," Gaster said, bowing his head as he pushed Sans forward. "I must ask for a favor..."

"You must be Sans," Asgore said, touching the young skeleton's head. "And this must by Papyrus."

Sans was still cradling his baby brother as Asgore bent down for a closer look. "yep..."

"Toriel," he called. "Why don't you show young Sans the library. I hear he is quite the book worm..."

Another goat monster stepped forward and Sans blushed. She was very beautiful. Toriel took the hand that wasn't cradling the crying baby and led Sans away. "Knock knock..."

Sans blinked and then found himself answering, "Who's there?"

"Boo." A small smile was beginning to stretch across Toriel's face.

"Boo who?"

"Aw come on, Papyrus is already crying… not you too..." Toriel teased and Sans found himself chuckling.

Gaster had told Sans that living in the country was safer for him and his little brother when he'd left them in the care of the king and queen. He and Papyrus weren't like other monsters. Their magic was… different. They was different.

Sans was still young but he knew what that meant. Once the shock wore off, Sans knew exactly what had happened. The mother of that poor human child was right. Sans had killed him. He didn't know why or how and Gaster was hardly around to answer any questions. And how could Toriel or Asgore ever understand when they'd never ripped out a human soul?

Papyrus was the only other monster like him and the only monster who would be able to understand. Not that Sans EVER wanted Papyrus to understand how he was feeling. No… Papyrus was too perfect and innocent. He would protect Papyrus at all costs. He would never let Papyrus near a human.

And so, little Sans shut himself off from the world. Sure, he'd laugh at Toriel's jokes. He'd play with the other kids, but never ever show his true colors or his true powers to them. While the other kids in the country practiced battling with the king, Sans would half heartedly toss bones at his opponents, unwilling to unleash his real power again. Not that he could kill the other monsters like he had the human. But it was Sans' deepest shame and he could never let anyone else know what he'd done. Gaster and Asgore and Toriel were already three monsters too many.

It wasn't until another five years had passed and Papyrus was old enough to walk and talk and start training that it happened to Sans again. He was sat on a grassy hill watching his little brother train with an older monster named Undyne. Watching Papyrus was one of the only things that brought him true happiness. Sans smiled with pride as Papyrus conjured a small bone out of thin air. As it floated above the young skeleton's hand, he beamed at the sight, "SANS! LOOK SANS! I HAVE MADE A BONE!"

Sans smiled at his little brother, "that's great bro… but pay attention!"

Just as he said it, one of Undyne's spears came whizzing past Papyrus' skull. "HEY! NO FAIR! YOU WILL NOT BEST THE GREAT PAPYRUS!"

Sans chuckled at his brother. So cute.

"SANSSSS..."

"yeah?" Sans looked up at his brother and it took a moment before he realized it hadn't been his brother's voice that had called his name. He dropped the blade of grass as the world turned black and white. Shit. No. Not again. The sound of Undyne's laughter and Papyrus' annoyance faded away to silence. In fact, he couldn't even SEE Papyrus or Undyne or anyone anymore for that matter.

It took a moment before Sans finally saw it. Far far in the distance, there was something glittering and Sans felt the bones in his chest constrict. It was happening again. He could hear it more clearly now, calling his name over and over and over. This time, the voice calling him was different before. Last time it had been deeper, more masculine. Definitely a boy's voice.

But now the voice chanting his name was higher and sweeter. He stood up, his feet carrying him in the direction of the voice. After a few steps, he realized the voice wasn't chanting. It was _singing._ And god, it was the prettiest thing he'd ever heard. He couldn't have stopped himself if he'd tried. He let himself be lead by the voice and the shimmering heart. He walked for what must have been over an hour, through the deep woods until he finally came out on the other side. There was the heart, underneath a tree, floating about a foot off the ground.

It took all of Sans' willpower to stay where he was. He watched the soul for hours and it was almost torture to have to listen to that voice calling for him. Finally, the heart floated a little higher and he watched it walk towards a house not far from the tree. After a while, the world became colorful again and Sans went home.

He went back every day that week. He knew more about the nature of human souls now that he was a little older. When the world went black and white, all he could see was the soul, but he that soul was encased in an actual human. A human he didn't _want_ to kill even if it seemed like her voice was begging him for it. And what a beautiful voice it was, begging for him. The thought made Sans blush.

He wanted to see the human.

He'd been watching her soul for so long that he knew her routine by heart now. But he didn't want to scare her. If she saw him, she would scream. He would be in trouble, or worse, dead. And then no one would be around to watch Papyrus. Sans left early that morning, before the sun was even up, and made the trek to his human's favorite tree. He climbed high enough into the branches that he hoped she wouldn't be able to see, and just waited.

First, he needed to figure out how to stop the world from turning to black and white. He'd gotten so lazy with his magic, he didn't even know where to begin. He'd been sitting in his tree when he heard the whispering of his name and he could see the edges of his vision growing black and white. NO… he concentrated as hear as he could, whisps of blue magic floating out of his fingertips.

His magic looked almost like streams of water, twisting and curling from his fingertips. And then he saw her. A human girl, about the same size as Sans, with almost no hair on her head. She was humming a song as she walked towards the tree, a book tucked under her arm. He watched as the blue streams of his magic spun around her and they were gone.

Sans had no idea what he'd done or if he could ever do it again. But at least now he could see the human. She didn't look like the humans from the story books he read Papyrus at bedtime, but Sans thought she was pretty. For a human, anyway.

He sat in the tree, still as could be in hopes that she wouldn't see him. The girl sat down and opened a book on her lap, her humming coming to a stop as she began to read aloud from her book. Sans froze. Did she know he was there? After a few minutes, he relaxed. He didn't think so. When an old lady came and called her away, Sans took it as his cue to leave and went back home to where Papyrus was telling him excitedly how he'd landed a hit on Undyne for the first time.

'tomorrow,' Sans thought. 'I'll bring a book too.'

And that's how it went. Instead of training, or studying, Sans would take a book and go to the tree and wait for his human. Some days she didn't come. And some days no matter how hard Sans tried, he couldn't stop the world from going black and white. On those days, he didn't get too close.

Sans' routine didn't go unnoticed by Papyrus. And Papyrus had enough of his brother's laziness. When he saw Sans sneak out of his room before dawn, Papyrus was already dressed and ready to discover what his brother was up to. He trailed behind Sans, sneaking quietly. Or so he thought.

Sans, however, had known before he even left Dreemurr house that Papyrus was following him How could he not notice when Papyrus was like an elephant in a china shop? Papyrus was dressed in a bright red t-shirt, clomping around, and greeting every forest animal he came across in a loud whisper.

Finally, Sans couldn't take it anymore. "paps..."

"YES?" a voice called from about 30 feet behind him. "I MEAN… UM… RIBBIT?"

"come on, paps…i know it's you..." Sans almost wanted to laugh at his little brother's attempt.

"HOW DID YOU KNOW, BROTHER?" Sans said loudly as he sprinted to catch up.

"dunno…i guess a little froggy _toad_ me." Sans shrugged and Papyrus groaned at the pun.

"HMM I'LL HAVE TO WORK ON MY SNEAK ATTACK..." Papyrus said thoughtfully. He slowed his pace to walk in time with Sans. "WHERE ARE WE OFF TO?"

"nowhere special..." Sans said, shoving his hands in his jacket pockets. That answer seemed to disappoint Papyrus but he didn't say anything. Soon, they reached the clearing and Sans led his brother across it. "up here," he pointed to the tree and began climbing.

Papyrus followed him up and sat next to him on a thick tree branch. "WHAT ARE WE DOING?"

Sans leaned back so that he dangled upside down from the branch. "you know, just _hanging _out, bro."

"SAAAAANS," Papyrus whined but his attention was torn away from his brother's antics. He perked up. "DO YOU SEE THAT BROTHER?"

Sans blinked. Shit. Could Papyrus see the human's soul? This had been a terrible mistake, letting Papyrus come along.

"I SAID, DO YOU SEE THAT HUMAN, SANS?!" Papyrus exclaimed and Sans threw a hand over his little brother's mouth.

"Shhh..." Sans said and began conjuring his stream of blue magic and channeling it towards the little girl. It was almost second nature now, and Sans was sure it was some kind of protection magic. "i see her too bro..."

Papyrus watched what Sans were doing, and whispered loudly as the girl began to run downhill towards the tree, "DO ALL HUMANS SMELL LIKE THAT?"

Sans could smell it too. She smelled… nice. Like flowers and vanilla and… death. He didn't like to think it. It disturbed him a little that not only could he smell it, but that he liked it.

The human sat down and opened her book and began reading from it, which thrilled Papyrus. Sans could see his little brother bouncing excitedly as the girl read her story about a princess in a castle. Leave it to Papyrus to be entranced by a fairy tale.

About halfway through the story, the human closed her book and stood up. Sans knew that meant it was lunch time. Before Sans could even stop his brother, Papyrus had hopped down from the tree. "WAIT, HUMAN. THE STORY IS NOT FINISHED!"

"paps, no!" Sans jumped down too. They were in so much trouble! "lets go!" They needed to leave, NOW. He couldn't let the human hurt Papyrus. Even if he was fond of this particular human.

The girl was frozen, looking at them with wide eyes as Sans started pulling on Papyrus' arm. "Wait!" the girl finally spoke. "Are you… monsters?"

"WHY YES, HUMAN!" Papyrus said excitedly. "AND YOU ARE A HUMAN!"

"That is so COOL!" the girl gushed.

"WOWIE. DID YOU HEAR THAT SANS?" Papyrus bounced. "THE HUMAN THINKS I AM COOL. ISN'T THAT SWELL?"

Sans nodded, still looking at the human.

"HUMAN, WHERE IS YOUR HAIR? THE HUMANS IN MY PICTURE BOOKS HAVE LONG BEAUTIFUL HAIR..." Papyrus said, matter-of-factly.

The girl's face turned red and she covered her head with a free hand. "Oh, um. I'm sick so..."

Sans elbowed Papyrus and said, 'paps… _shave_ your stupid questions for later...' Papyrus groaned and Sans almost did too. That was bad. So bad. You could tell she was embarrassed and yet you had made a joke of it.

The girl blink and then grinned and Sans smirked back at her. "name's sans and this is my little bro papyrus."

"YES, I'M SURE WE'LL BE GREAT FRIENDS, ESPECIALLY IF YOU FINISH THAT WONDERFUL STORY!"

"Oh… I have to go eat lunch and rest. But maybe tomorrow?" the girl said hopefully.

"OH YES! WE WILL BE HERE, RIGHT SANS?"

"sure thing, bro..."

The next day, Sans made a flower crown from flowers Papyrus had collected while they waited for their new friend. When she arrived, Sans placed it on top of her head. "there ya go. now you look like the princesses in paps' books."

She blushed as she looked at him, but Sans could tell she was pleased and it made a faint blue blush spread over his cheekbones too. "COME SIT NEXT TO ME HUMAN!" Papyrus interrupted, patting the ground next to him.

_Present Day_

Sans was snapped out of his memories as he felt a small hand squeeze his phalanges. He looked down at Frisk. "hmm? what's up, kid? ready to go?" He looked down the mountain, out at the city in the distance before letting his vision go to black and white. Finally he found what he was looking for – like a pinprick miles away, a shimmering human soul.


End file.
